<!DOCTYPE html>
<script>
function test()
{
    if (!window.testRunner || !window.internals)
        return;

    testRunner.dumpAsText();
    document.body.offsetTop;
    internals.startTrackingRepaints(document);

    document.getElementById('left').style.top = '400px';
    document.getElementById('right').style.top = '400px';

    document.body.offsetTop;
    var layerTree = internals.layerTreeAsText(document, internals.LAYER_TREE_INCLUDES_INVALIDATIONS);
    internals.stopTrackingRepaints(document);
    document.getElementById('result').textContent = layerTree.indexOf('repaint') == -1 ? 'SUCCESS' : 'FAIL';
}

window.onload = test;
</script>

<style>
    #left, #right {
        position: absolute;
        top: 200px;
        backface-visibility: hidden;
    }
    #left {
        left: 0px;
    }
    #right {
        right: 0px;
    }
</style>

There should be no repaint when the divs are moved vertically.
<div id="left">Left</div>
<div id="right">Right</div>
<pre id="result"></pre>
